Dry spinning process



Patented Dec. 4, 1945 UNITED STATE s PATENT OFFICE 2,390,132 DRY SPINNING PROCESS Albert F.

Brandywine Hundre secondary aliphatic amine, and-thereafter spin- Smith and Halsey B. Stevenson,

6, Del., assignors to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application October 18, 1944,

, Serial N0. 559,232

Claims. (Cl. 1847.5)

olefin/vinyl organic ester interpoly-' ning the resultant solution. While filaments are thus produced readily, said filaments have limited utility on account of the fact that they tend to be brittle and have relatively low tenacities.

This invention has as an object the provision of hydrolyzed ethylene/vinyl organic ester interpolymer filaments which have been spun from solution and which have improved properties, particularly high tenacities and decreased brittleness. Additional objects will become apparent from the following description and claims.

These and other objects and advantages are accomplished according to the herein described invention which broadly comprises heating for a period of at least 5 hours at a temperature within the range of from its sticking temperature to C. below said sticking temperature in a taut condition, a filament, previously spun from solution, interpolymer of ethylene with a vinyl ester of a monocarboxylic acid having the general formula RCOOH, wherein R is of the group consisting of hydrogen atoms and hydrocarbon radicals, said acid being free from unsaturated linkages between acyclic carbon atoms and any carbom atom alpha to the carbon atom in the carboxyl group of said acid being attachedto at least one but not more than three carbon atoms, the. mol ratio of ethylene to vinyl organic ester prior to hydrolysis having been within the range of from l/1 to 5/1, and thereafter drawing the treated filament at least 100% of its original length.

A preferred embodiment of this invention comprises spinning from solution a substantially completely hydrolyzed ethylene/v nyl acetate interpolymer, the mol ratio of ethylene to vinyl acetate in said interpolymer prior to hydrolysis having been within the range of from 2/1 to 4/1, and immediately thereafter heating said filament for a period within the range of from 5 hours to 8 hours at a temperature within the range of from its sticking temperature to 10 below said sticking temperature, and then within two days of a substantially completely hydrolyzed I stretching in saturated drawing the resultant filament at least of its original length.

The following example, in which proportions are in parts by weight unless otherwise specified,

is given for illustrative purposes and is not intended to place any restrictions on the herein described invention:

Example An interpolymer of ethylene and vinyl acetate (of molar ratio of ethylene to vinyl acetate of 2.5/1) was prepared by the controlled addition of ethylene-at about 1000 atm. pressure and at about 65 C. to vinyl acetate containing a small amount of benzoyl peroxide catalyst. The ethylhydrolyzed in a benzene-methanol solution with excess caustic and the interpolymer was washed free of caustic and dried. A solution was prepared by dissolving 250 parts of the parts of trichloroethylene and 2'75 .parts of ethanol. This solution, which had a viscosity of 50 poises at 60 C., was spun through a multihole spinneret into a heated tube so that the solvent was removed from the filaments by passage through the tube. This yarn lacked strength and was shown by X-ray difiraction patterns to be unoriented. 7

A portion of the unoriented. yarn was heated at fixed length in air in an oven .at a temperature of -110" C. for 24 hours. It was then drawn in saturated steam at atmospheric pressure at a draw ratio of 8.33/1 to give an oriented yarn which had a tenacity of 5.4 g./d. at 7% elongation.

When a portion of the yarn was oriented by steam 'at atmospheric pressure at the maximum draw ratio which could be employed (7.5/ 1) but without any preheating, the drawn yarn had a tenacity of only 4.1 g./d. at 8% elongation.

The process of this 'inventionis applicable to any hydrolyzed interpolymer of ethylene with a vinyl ester of an organic acid having the general formula RCOOH, wherein R is of the group consisting of hydrogen atoms and hydrocarbon radicals, said acid being free from unsaturated linkages betweenacyclic carbon atoms and any carbon atom alpha to the carbon atom in the carboxyl group of said acid being attached to at least one but not more than three carbon atoms,

provided the mol ratio of ethylene to vinyl organic ester in said interpolymer prior to hydrolysis was within the range of from l/l to 5/1.

I hydrolyzed ethylene/ vinyl acetate interpolymer in a mixture of 1000 of the superior products had therewith, we prefer to employ an interpolymer of ethylene with a vinyl ester of an organic acid having the general formula CnHai COOH, wherein n is a positive integer within the range of from 1 to 3.

Appreciable effects are had when the mol ratio of ethylene to vinyl organic ester in the interpolymer prior to hydrolysis is as low as 1/ 1, and also when it is as high as /1. However, the filaments obtained according to the process of this invention have markedly superior strength characteristics when the mol ratio of ethylene to vinyl organic ester in said interpolymer prior to hydrolysis is within the range of from 2/1 to 4/1.

As shown in the example, the interpolymerization of the vinyl ester with ethylene can be carried out under superatmospheric pressure in the presence of a peroxygen-type polymerization catalyst. The resulting interpolymer-is hydrolyzed by treatment in solution with an alkali dissolved in a lower alcohol or in aqueous solution. For preparing filaments, 'the resulting hydrolyzed' interpolymer should be at least 80% hydrolyzed and preferably substantially completely hydrolyzed.

For the production of the improved hydrolyzed ethylene/vinyl ester filaments by this invention it is necessary that the filaments be prepared by spinning from solution in solvents, such astrichloroethylene-ethanol, primary aliphatic alcohols, primary or secondary aliphatic amines, and that they be heat-treated such as under conditions previously described before being subjected to a substantial amount of orientation. It has been found that the process described actually produces a loss of strength when applied to filaments obtained by spinning the moltenpolymer (melt-spinning). It has been shown unlikely that the improvement obtained from the solution-spun (dry-spun) yarn is due to retention of solvent since the solvent is substantially completely removed before the heating has progressed for more than a limited period.

For best results, the filaments should be treated by the described process before they have been permitted .to age appreciably. If the filaments have been allowed to remain at room temperature for long periods, e. g., for periods of greater than 4 days, the amount of improvement is not as great. It is preferred that the filament be subjected to the heat treatment less than two days after its preparation and for maximum results the filament employed should be used as soon as possible after it has been formed. Similarly, the. heat-treated filament should be drawn within a short time after the heat treatment. This orientation or drawing should usually take place within a time of less than two days after the heat treatment to obtain the maximum strength of the resuiting fibers. It has been found that soaking the filament in water after the heat treatment and prior to drawing gives an oriented filament-having strength.

Th temperature of the heat treating operation is critical for the preparation of strong filaments. The operable temperatu es for the heat treatment of the hydrolyzed ethylene/vinyl ester interpolymer filaments are those within the range of from 20 C. below the sticking temperature of the filaments and said sticking temperature. In general, the temperature at which filaments of the yarn will stick together (which temperature is approximately that of the sintering temperature and slightly less than the softening temperature or the zero tensile strength temperature of the filaments) for hydrolyzed interpolymers of ethylene and vinyl acetate of molar ratio of ethylene to vinyl acetate of between 2/1 and 3.5/1 is usually between 108-1l2 C. The maximum strengths of the resulting filaments may be obtained by heat"'treating within the range of from 10 C. below the sticking or sintering temperature and the sintering temperature. For example, for a hydrolyzed ethylene/vinyl acetate interpolymer of molar ratio of ethylene/vinyl acetate of 2.5/1, the sticking temperature is about 108-110 C. and the strength of the resulting filament after heat treatment at 105- 107 C. was found to be higher than when the heat treatment was carried out at a temperature of 101-103 C. Heat treatment at temperatures which are 25 C. or more below the sticking point of the filament has little effect on improving the properties of the resulting filaments. When temperatures of within 2 or 3 C.

of the sticking temperature of the filament are employed, care must be taken to prevent local overheating with resulting softening or melting of the filament.

The heat treatment ordinarily requires a time of at least 5 hours. It is preferred that the time be about 8 hours, while periods of time longer than 8 hours have not been found to eifect further improvement in properties.

The heat treatment can be carried out in any desired manner. For example, steam, air, oil or other types of baths may be employed. In general, the heating is most advantageously carried outby the use of an air-oven regulated at the desired temperature.

The orientation of the filament may be readily carried out by stretching or. tensioning the filament under a tension insuflicient to break the orientable polymeric filament. For example, the drawing may be readily effected by maintaining a speed diflerential between the drawing and feeding rolls when the filament is rewound from a roll. A higher ratio of the drawing to the feeding roll results in an increase in the tenacity of the filament above that which may otherwise be attained. Thus, the heat treatment by the method described in the example resulted in an increase in draw ratio to as high as 8.3/1 while draw ratios of only .5/ could be used without the heat treatment. The tenacity increases in general are 0.5/1.5 g./d. In any case, the draw ratio used in the orientation is at least 2/1, or on a percent basis, at least Heat treatment after the tensioning or orienting operation of hydrolyzed ethylene/vinyl ester filaments such as those employed in the treatment of cellulose acetate filaments does not bring about substantial improvement in the properties of these hydrolyzed interpolymer filaments.

In addition to the beneficial results on filaments obtained by heat treatment as described above, heat treatment of unoriented films and as iousa .molded objects of hydrolyzed ethylene/vinyl organic ester interpolymers also leads to remarkable improvement. Heat, treated films have higher tensile strength, higher elongation,'much.

greater tear strength, and greater toughness at low temperatures than films not subjected to the heat treatment. The properties of extruded tubing and injection or compression molded objects can also be improved by this method: In the case of films and molded objects, somewhat ,higher temperatures can often be used than for filaments, since slight softening of such objects is not necessarily objectionable. Temperaturesas high as 120 C. may be desirable in some instances. The beneficial eifects of high-temperatures on the properties of hydrolyzed ethylene/vinyl organic interpolymer films can also be obtained by the expedient of casting the films at temperatures near the softening po nt of the olymer. For this purpose the solvent used in casting should preferably boil at a temperature higher than the casting temperature. Suitable combinations of aromatic hydrocarbons and alcohols, for example, a solvent mixture containing 40%xylene and 60% isoamyl alcohol, boiling at 126 C., have been found to be particularly useful. Films cast at 110-120 C. from such a solvent have much better properties than films cast, for example, at 60-70 C. The properties of films cast at temperatures near the softening point can be further improved by additional heat treatment.

The improved filaments of this invention find use in the production of fabrics, cords, staple fibers, etc. Because of the increased tenacity of the filaments in conjunction with the other properties of the hydrolyzed ethylene/vinyl organic ester interpoiymers, the fibers are especially useful in the manufacture of i hosiery, ropes, woven belting, fishing lines, etc.

As many apparentlywidely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that we do not limit ourselves to the specific embodiments thereof except as defined in the appended claims. c

Having describedthe Present invention, the following is claimed as new and useful:

1. The process for obtaining an improved dryspun hydrolyzed ethylene/vinyl organic ester interpolymer filament, which comprises heating for a period of at least five hours at a, temperature within the'range of from its sticking temperature to 20 0. below said sticking temperature in a taut cbndition, a filament, previously spun from solution, of a hydrolyzed interpolymer of ethylene with a-vinyl ester of a monocarboxylic acid having the general formula RCOOH, wherein R is of the group consisting of hydrogen atoms and hydrocarbon radicals, said acid being free from unsaturated. linkages between acyclic carbon atoms and any carbon atom alpha to the carbon atom in the carboxyl group of said,

acid being attached to at least one but not more than three carbon atoms, the mol ratio of ethylene to vinyl organic ester in said interpolymer prior to hydrolysis having been within the range treated filament at least 110% of its original length.

2. The process forobtaining an improved dryspun hydrolyzed ethylene/vinyl organic ester interpolymer filament, which comprises heatin for a period of at least five hours at a temperature withinthe range of from its sticking temperature to 20 0. below said sticking temperature in a taut condition,' a filament, previously spun from solution, of a hydrolyzed interpolymer of ethylene with a vinyl ester of a monocarboxylic acid having the general formula C1iH21t+1COOH, wherein n is a positive integer within the range of 'from 1 to 3, the mol ratio of ethylene to vinyl organic ester in said interpolymer, prior to hydrolysis having been within the range of from 1/1 to 5/1, and thereafter drawing the treated filament at least 100% of its original length.

3. The process for obtaining an improved dryspun hydrolyzed ethylene/vinyl acetate inter-.

polymer filament, which comprises spinning a solution of a substantially completely hydrolyzed interpolymer of ethylene with vinyl acetate, the

mol ratio, of ethylene to vinyl acetate in said interpolymer prior to'hydrolysis having been within the range of from 1/1 to 5/l, within four days thereof heating the resultant filament in a taut condition fora period of at least five hours at a temperature within the range of from its sticking temperature to 20 C. below said sticking temperature, and thereafter, within two days of said heating operation, drawing the treated filament at least 100% of its original length.v

,4. The process for obtaining an improved dryspun hydrolyzed ethylene-lvinyl acetate interpolymer filament, which comprises spinning a solution of a substantially completely-hydrolyzed interpolymer of ethylene with vinyl acetate, the

40 mol ratio of ethylene to vinyl acetate in said interpolymer prior to hydrolysis having been within the range of from 1/1 to 5/1, within two days thereof heating the resultant filament in a taut condition for a period within the range of from 5 to 8 hours at a temperature within the range of from its sticking temperature to 20 C. below said sticking temperature, and thereafter, with in two days of said heating operation, drawing the treated filament at least of its original length.

5. The proces for obtaining an improved dryspun hydrolyzed ethylene-vinyl acetate interpolymer filament, which comprises spinning a solution of a substantially completely hydrolyzed interpolymer of ethylene with vinyl acetate, the.

,mol ratio of ethylene to vinyl acetate in said interpolymer prior to hydrolysishaving been within the range of from 2/1 to 4/1, and immediately thereafter heating the resultant. filament in a taut condition for a period within the range of from 5 to 8 hours at a temperature with- J in the range ofv from its sticking temperature to sticking temperature. and thereafter, within two days of said heatin'g'opeh ation, drawing the treated filament at least 100% i" of its original leiig'th.-v

10 C. below said I ALBERT n-sMrrn. s'rEvENsoN-g 

